Adhesion promoter and ink composition

ABSTRACT

An ink composition and an adhesion promoter are provided. The adhesion promoter is suitable for production while remaining the stronger adhesion. The adhesion promoter is formed by the reaction of at least one alpha hydroxy acid, at least one alpha hydroxy acid ester, and a polymer having hydroxyl group, amino group, carboxyl group, or a combination thereof with a metal alkoxide. By combining the renewable and green alpha hydroxy acid and safer plasticizing alpha hydroxy acid ester, and the polymer as reagents to react with the metal alkoxide, the eco-friendly and non-toxic adhesion promoter with superior adhesion for use in ink composition can be obtained. The ink composition includes the adhesion promoter, a pigment, a polymeric binder, and a solvent for the polymeric binder. The ink composition is odorless and colorless, and shows good wet crinkle resistance. Especially, the ink composition is suitable for printing on the food package.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to U.S. Provisional Application Ser.No. 62/401,905, filed Sep. 30, 2016, which is herein incorporated byreference.

BACKGROUND Field of Invention

The present invention relates to an ink composition and an adhesionpromoter. More particularly, the present invention relates to an inkcomposition and an adhesion promoter for use in ink composition, whereinthe adhesion promoter includes a reaction product of a metal alkoxide, amixture of at least one alpha hydroxy acid and at least one alphahydroxy acid ester, and at least one polymer having hydroxyl group,amino group, carboxyl group, or a combination thereof.

Description of Related Art

Adhesion promoters have long been used in inks to promote adhesionproperties to enable the inks to adhere to a variety of substrates andthus meet requirements of customers and end-users.

However, in some printing ink formulation processes, adhesion promoterssuch as titanium acetylacetonates tend to impart undesirable by-productsto the ink. These by-products may have undesired yellow color and odorand thus adversely influence the resulting inks. Moreover, the toxicacetylacetone derivative ingredient is not suitable for being printed onfood package due to potential migration problem. Based on above, it isrequired adhesion promoters with superior adhesion and safety to satisfythe current industrial needs.

SUMMARY

The present disclosure provides an adhesion promoter. The adhesionpromoter includes a reaction product of a metal alkoxide, a mixture ofat least one alpha hydroxy acid and at least one alpha hydroxy acidester, and at least one polymer having hydroxyl group (—OH), amino group(—NH₂), carboxyl group (—COOH), or a combination thereof. Morespecifically, by combining the renewable and green alpha hydroxy acidand safer plasticizing alpha hydroxy acid ester, and the polymer asreagents to react with the metal alkoxide, the eco-friendly andnon-toxic adhesion promoter with superior adhesion for use in inkcomposition can be obtained. The metal alkoxide has a formula ofM(OR₁)(OR₂)(OR₃)(OR₄), wherein M is titanium, zirconium, or aluminum,and R₁, R₂, R₃, and R₄ are independently C₁ to C₈ alkyl group. The alphahydroxy acid is selected from the group consisting of glycolic acid,lactic acid, malic acid, tartaric acid, and citric acid. The alphahydroxy acid ester is selected from the group consisting of glycolicacid ester, lactic acid ester, malic acid ester, tartaric acid ester,and citric acid ester.

In some embodiments, the glycolic acid ester has a formula ofCH₂OH(COOR₅), and R₅ is C₂ to C₆ alkyl group.

In some embodiments, the lactic acid ester has a formula ofC₂H₄OH(COOR₆), and R₆ is C₂ to C₆ alkyl group.

In some embodiments, the malic acid ester has a formula ofC₂H₃OH(COOR₇)(COOR₈), R₇ and R₈ are independently H atom or C₂ to C₆alkyl group, and one of R₇ and R₈ is an alkyl group.

In some embodiments, the tartaric acid ester has a formula ofC₂H₂(OH)₂(COOR₉)(COOR₁₀), R₉ and R₁₀ are independently H atom or C₂ toC₆ alkyl group, and one of R₉ and R₁₀ is an alkyl group.

In some embodiments, the citric acid ester has a formula ofC₃H₄OH(COOR₁₁)(COOR₁₂)(COOR₁₃), R₁₁, R₁₂ and R₁₃ are independently Hatom or C₂ to C₆ alkyl group, and one of R₁₁, R₁₂ and R₁₃ is an alkylgroup.

In some embodiments, the mixture further comprises water.

In some embodiments, the polymer is selected from the group consistingof polyol, polyurethane, polyurethane-urea, polyamide, polyacrylate,ketone-formaldehyde copolymer, nitrocellulose, polyvinyl alcohol,ketonic resin, alkyd, and polysaccharide.

In some embodiments, the at least one polymer having the hydroxyl grouphas a hydroxyl number of from about 30 mg KOH/g to about 500 mg KOH/g.

In some embodiments, a ratio of a number of the hydroxyl group of the atleast one polymer having the hydroxyl group to a number of M of themetal alkoxide is 0.25-4:1.

In some embodiments, the at least one polymer having the amino group hasan amine value of from about 3.5 mg KOH/g to about 15 mg KOH/g.

In some embodiments, a ratio of a number of the amino group of the atleast one polymer having the amino group to a number of M of the metalalkoxide is 0.25-4:1.

In some embodiments, the mixture has a carboxylic acid number of fromabout 50 mg KOH/g to about 400 mg KOH/g.

In some embodiments, a ratio of a total mole of the at least one alphahydroxy acid and the at least one alpha hydroxy acid ester to a mole ofthe metal alkoxide is 0.2 to 4:1.

The present disclosure provides an ink composition. The ink compositionincludes a pigment, a polymeric binder, a solvent for the polymericbinder, and an adhesion promoter including a reaction product of a metalalkoxide, a mixture of at least one alpha hydroxy acid and at least onealpha hydroxy acid ester, and at least one polymer having hydroxyl group(—OH), amino group (—NH₂), carboxyl group (—COOH), or a combinationthereof. The metal alkoxide has a formula of M(OR₁)(OR₂)(OR₃)(OR₄),wherein M is titanium, zirconium, or aluminum, and R₁, R₂, R₃, and R₄are independently C₁ to C₈ alkyl group. The alpha hydroxy acid isselected from the group consisting of glycolic acid, lactic acid, malicacid, tartaric acid, and citric acid. The alpha hydroxy acid ester isselected from the group consisting of glycolic acid ester, lactic acidester, malic acid ester, tartaric acid ester, and citric acid ester.

In some embodiments, the adhesion promoter is present at a concentrationof from 1% to 20% by weight, based on the total weight of the inkcomposition.

In some embodiments, the polymeric binder has at least one functionalgroup selected from the group consisting of hydroxyl group (—OH), aminogroup (—NH₂), carboxyl group (—COOH), cyanate group (—NCO), and estergroup.

These and other features, aspects, and advantages of the presentinvention will become better understood with reference to the followingdescription and appended claims.

It is to be understood that both the foregoing general description andthe following detailed description are by examples, and are intended toprovide further explanation of the invention as claimed.

DETAILED DESCRIPTION

The use of examples anywhere in this specification including examples ofany terms discussed herein is illustrative only, and in no way limitsthe scope and meaning of the invention or of any exemplified term.Likewise, the invention is not limited to various embodiments given inthis specification.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this invention belongs. It will befurther understood that terms, such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art and thepresent disclosure, and will not be interpreted in an idealized oroverly formal sense unless expressly so defined herein.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a,” “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising”, or “includes” and/or “including” or “has” and/or“having” when used in this specification, specify the presence of statedfeatures, integers, steps, operations, elements, and/or components, butdo not preclude the presence or addition of one or more other features,integers, steps, operations, elements, components, and/or groupsthereof.

The present disclosure provides an ink composition and an adhesionpromoter for use in ink composition. More specifically, the adhesionpromoter is for formulating ink composition. In some embodiments, theadhesion promoter is used in printing ink composition. The printing inkcomposition may be used for printing paper, foil, and plasticsubstrates, especially the plastic films for food packaging or flexiblesubstrates. The material of plastic substrate includes but not limitedto polyester, polyethylene, polypropylene, and co-extruded polyolefin.

Compared to paper or foil, the adhesion between printing ink compositionand plastic films is weaker due to their extreme low surface energycharacteristics. Therefore, the printing ink composition must need anadhesion promoter which can improve the adhesion on plastic films forindustrial production.

Both physical and chemical interaction induced by adhesion promoters canenhance the adhesion between printing ink and plastic films. Theadhesion promoter improves the adhesion by providing the chemical bondformation between the plastics films and printing ink. This chemicalreaction is also called crosslinking reaction. A metal alkoxide can bechosen as adhesion promoter because of the chemical bond formationability with oxygen-rich species (e.g. the binder in printing ink).However, the metal alkoxide is too reactive with the oxygen-richspecies; therefore, the oxygen-rich species added with the metalalkoxide is too stable and has poor fluidity. Accordingly, the metalalkoxide cannot be used as adhesion promoter alone. In order to solvethe above issues, the metal alkoxide can be chelated by at least oneligand formed from a mixture of at least one alpha hydroxy acid and atleast one alpha hydroxy acid ester and reacted with at least one polymerhaving hydroxyl group (—OH), amino group (—NH₂), carboxyl group (—COOH),or a combination thereof to strike a balance between reactivity andstability after mixing with the printing ink. The alpha hydroxy acid andalpha hydroxy acid ester are lower toxicity substance. It statesdifferent combinations of the alpha hydroxy acid, the alpha hydroxy acidester, and the polymer can be chosen according to the need offormulator. The reaction product of the metal alkoxide, the at least onealpha hydroxy acid, the at least one alpha hydroxy acid ester, and thepolymer, can retain the adhesion-improving ability and lower toxicity bycontrolling the residual alkoxy group on metal and the carboxylic acidgroups in the mixture. Also, controlling of the alkyl group on the alphahydroxy acid ester can increase the compatibility to the plastic filmsand polymer binders in printing ink.

The adhesion promoter of the present disclosure includes a reactionproduct of a metal alkoxide, an acid ester mixture including at leastone alpha hydroxy acid and at least one alpha hydroxy acid ester, and atleast one polymer having hydroxyl group (—OH), amino group (—NH₂),carboxyl group (—COOH), or a combination thereof. The at least one alphahydroxy acid includes one or more alpha hydroxy acids. The at least onealpha hydroxy acid ester includes one or more alpha hydroxy acid esters.The at least one polymer includes one or more polymers.

In other words, the adhesion promoter is formed by reacting the metalalkoxide, the at least one alpha hydroxy acid, the at least one alphahydroxy acid ester, and the polymer having hydroxyl group, amino group,carboxyl group, or a combination thereof. In some embodiments, the stepof reacting the metal alkoxide, the at least one alpha hydroxy acid, theat least one alpha hydroxy acid ester, and the polymer is performed at atemperature from about 20° C. to about 200° C. In some otherembodiments, the temperature is from about 20° C. to about 100° C. Insome embodiments, the polymer is a solvent-based polymer. In someembodiments, before reacting the metal alkoxide, the at least one alphahydroxy acid, the at least one alpha hydroxy acid ester, and thepolymer, the polymer is dissolved in a solvent such as an alcohol, anester, a ketone, or a hydrocarbon. For example, the solvent includesethanol, propan-1-ol, isopropanol, n-butanol, ethyl acetate, propylacetate, n-butyl acetate, acetone, butanone, cyclohexanone, n-hexane orn-heptaneor a combination thereof. In some embodiments, the polymer ispresent at a concentration of from 20% to 70% by weight, based on thetotal weight of the solvent and the polymer.

The metal alkoxide has a formula of M(OR₁)(OR₂)(OR₃)(OR₄), wherein M istitanium, zirconium, or aluminum, and R₁, R₂, R₃, and R₄ areindependently C₁ to C₈ alkyl group. More specifically, R₁, R₂, R₃, andR₄ are independently linear or branched alkyl group. In someembodiments, R₁, R₂, R₃, and R₄ are independently methyl, ethyl,n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, n-pentyl,tert-pentyl, neopentyl, isopentyl, sec-pentyl, 3-pentyl, hexyl, heptyl,or octyl. In some embodiments, R₁, R₂, R₃, and R₄ are independentlypropyl or butyl, and R₁, R₂, R₃, and R₄ include at least one propyl andat least one butyl; therefore, the metal alkoxide is propyl butyl metalalkoxide. In some other embodiments, R₁, R₂, R₃, and R₄ are n-propyl,and thus the metal alkoxide is tetra n-propyl metal alkoxide. In stillsome other embodiments, R₁, R₂, R₃, and R₄ are isopropyl, and thus themetal alkoxide is tetra isopropyl metal alkoxide.

The alpha hydroxy acid is selected from the group consisting of glycolicacid, lactic acid, malic acid, tartaric acid, and citric acid. The alphahydroxy acid ester is selected from the group consisting of glycolicacid ester, lactic acid ester, malic acid ester, tartaric acid ester,and citric acid ester.

In some embodiments, the glycolic acid ester has a formula ofCH₂OH(COOR₅), and R₅ is C₂ to C₆ alkyl group. In some embodiments, thelactic acid ester has a formula of C₂H₄OH(COOR₆), and R₆ is C₂ to C₆alkyl group. In some embodiments, the malic acid ester has a formula ofC₂H₃OH(COOR₇)(COOR₈). R₇ and R₈ are independently H atom or C₂ to C₆alkyl group, and one of R₇ and R₈ is an alkyl group. In someembodiments, the tartaric acid ester has a formula ofC₂H₂(OH)₂(COOR₉)(COOR₉). R₉ and R₁₀ are independently H atom or C₂ to C₆alkyl group, and one of R₉ and R₁₀ is an alkyl group. In someembodiments, the citric acid ester has a formula ofC₃H₄OH(COOR₁₁)(COOR₁₂)(COOR₁₃). R₁₁, R₁₂ and R₁₃ are independently Hatom or C₂ to C₆ alkyl group, and one of R₁₁, R₁₂ and R₁₃ is an alkylgroup. In some embodiments, R₅ to R₁₃ are independently linear orbranched alkyl group. In some embodiments, R₅ to R₁₃ are independentlyethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl,n-pentyl, tert-pentyl, neopentyl, isopentyl, sec-pentyl, 3-pentyl, orhexyl.

In some embodiments, the carboxylic acid number of the acid estermixture is in the range of from about 50 mg KOH/g to about 400 mg KOH/g.In some embodiments, a mole ratio of the acid ester mixture to the metalalkoxide is 0.2 to 4:1.

In some embodiments, the polymer having hydroxyl group (—OH), aminogroup (—NH₂), carboxyl group (—COOH), or a combination thereof isselected from the group consisting of polyol, polyurethane,polyurethane-urea, polyamide, polyacrylate, ketone-formaldehydecopolymer, nitrocellulose, polyvinyl alcohol, ketonic resin, alkyd, andpolysaccharide. For example, the polyol is polyester polyol or polyetherpolyol. In some embodiments, the at least one polymer has the hydroxylgroup and has a hydroxyl number of from about 30 mg KOH/g to about 500mg KOH/g. In some embodiments, the at least one polymer has the hydroxylgroup, and a ratio of a number of the hydroxyl group of the at least onepolymer to a number of M of the metal alkoxide is 0.25-4:1. In someembodiments, the at least one polymer has the amino group and has anamine value of from about 3.5 mg KOH/g to about 15 mg KOH/g. In someembodiments, the at least one polymer has the amino group, and a ratioof a number of the amino group of the at least one polymer to a numberof M of the metal alkoxide is 0.25-4:1.

It is noted that the adhesion promoter of the present disclosureincludes the reaction product of the metal alkoxide, the acid estermixture, and the polymer. More specifically, after the reaction of themetal alkoxide, the acid ester mixture, and the polymer, the ingredientin the acid ester mixture would bind to the metal atom and the polymerwould also bind to the metal atom.

For example, when one carboxylic acid group on the citric acid isreacted with the metal alkoxide, the metal alkoxide loses one alkoxygroup (for example, OR₁, OR₂, OR₃, or OR₄), and the citric acid losesone hydrogen atom of the carboxylic group and then bonds with the metalatom of the metal alkoxide. Further, for example, when the tri-alkylcitrate is reacted with the metal alkoxide, the tri-alkyl citrate maybond with the metal atom of the metal alkoxide with its hydroxyl groupsby transesterification. More specifically, the alkoxy group of the metalalkoxide may be replaced with the hydroxyl group of the tri-alkylcitrate. The way of the mono-alkyl citrate and the di-alkyl citratebinding with the metal alkoxide can be inferred from the descriptionsabove, and therefore is not repeated herein. It is noted that one metalalkoxide can react with one reactant or at least two reactantssimultaneously. If the metal alkoxide react with at least two reactants,the at least two reactants can be different. For example, the alphahydroxy acid is citric acid, and the at least one alpha hydroxy acidester includes mono-alkyl citrate, di-alkyl citrate, tri-alkyl citrate,or a combination thereof. In some embodiments, the metal alkoxide reactswith the citric acid and the mono-alkyl citrate simultaneously. In someother embodiments, the metal alkoxide reacts with the mono-alkyl citrateand the di-alkyl citrate simultaneously. In still some otherembodiments, the metal alkoxide reacts with the citric acid, themono-alkyl citrate, and the di-alkyl citrate simultaneously.

Moreover, when the polymer having hydroxyl group (—OH), amino group(—NH₂), carboxyl group (—COOH), or a combination thereof is reacted withthe metal alkoxide, the alkoxy group of the metal alkoxide may bereplaced with the hydroxyl group, the amino group, the carboxyl group ofthe polymer. The metal alkoxide may react with at least two polymers. Insome embodiments, the at least two polymers can be different.

In some embodiments, the acid ester mixture further includes water. Morespecifically, the adhesion promoter includes a reaction product of ametal alkoxide and an acid ester mixture including at least one alphahydroxy acid, at least one alpha hydroxy acid ester, the polymer, andwater. It is noted that the compounds having alkoxy group which arereaction products of the metal alkoxides, the acid ester mixture, andthe polymer, or the metal alkoxides, may react with water, and thus thealkoxy groups of the compounds or the metal alkoxides may be replacedwith hydroxyl groups (—OH). Specifically, the water may promote thehydrolysis and polymerization of the metal alkoxides, and the alphahydroxy acid ester is not hydrolyzed by the water due to the reactionrate difference. After that, the hydrolyzed product can further reactwith another metal alkoxides or hydrolyzed metal alkoxides to form alarger molecule, together with the loss of water or alcohols. Thisreaction is a condensation reaction. Accordingly, the reaction productof the metal alkoxide and the acid ester mixture including water mayinclude many kinds of condensation compounds. The above condensationreaction can be further illustrated by the following example. Forexample, after two compounds having a formula of M(L₁)(L₂)(L₃)(OR) reactwith water, two compounds having a formula of M(L₁)(L₂)(L₃)(OH) areformed, wherein L₁, and L₂, and L₃ are independently a ligand formedfrom a citric acid, a mono-alkyl citrate, a di-alkyl citrate, atri-alkyl citrate, or a polymer having hydroxyl group, amino group,carboxyl group, or a combination thereof, and OR is an alkoxy group.After that, the two compounds having a formula of M(L₁)(L₂)(L₃)(OH) maycombine to form M(L₁)(L₂)(L₃)-O-M(L₁)(L₂)(L₃) and water.

The ink composition of the present disclosure includes a pigment, apolymeric binder, a solvent for the polymeric binder, and an adhesionpromoter. In some embodiments, the adhesion promoter is present at aconcentration of from 1% to 20% by weight, based on the total weight ofthe ink composition.

In the present disclosure, the ink composition includes one or morepigments. The pigments may be inorganic pigment or organic pigment. Insome embodiments, the pigment is TiO₂. In some embodiments, thepolymeric binder has at least one functional group selected from thegroup consisting of hydroxyl group (—OH), amino group (—NH₂), carboxylgroup (—COOH), cyanate group (—NCO), and ester group. For example, thepolymeric binder includes polyester resin, polyamide resin, polyurethaneresin, polyurethane-urea resin, nitrocellulose, polyacrylate resin,polyol resin, polyester polyol resin, polyether polyol resin, ketonicresin, ketone-formaldehyde copolymer, polyvinyl alcohol, or acombination thereof. In some embodiments, the polyacrylate resin ispolymethylmethacrylate (PMMA). In some embodiments, the solvent for thepolymeric binder includes alcohol, ester, ketone, hydrocarbon solvent,or a combination thereof. For example, the alcohol is ethanol,propan-1-ol, isopropanol, or n-butanol. For example, the ester is ethylacetate, propyl acetate, or n-butyl acetate. For example, the ketone isacetone, butanone, or cyclohexanone. For example, the hydrocarbonsolvent is n-hexane or n-heptane.

The disclosure is further illustrated by the following examples, whichare not to be construed as limiting this disclosure in scope or spiritto the specific procedures herein described. It is to be understood thatthe examples are provided to illustrate certain embodiments and that nolimitation to the scope of the disclosure is intended. It is to befurther understood that resort may be had to various other embodiments,modifications, and equivalents thereof which may suggest themselves tothose skilled in the art without departing from the spirit of thepresent disclosure and/or scope of the appended claims.

Example 1: Preparation of Adhesion Promoter (Product 1) Including aReaction Product of Tetra n-Propyl Zirconate, Citric Acid Ester Mixture,and Resin VariPlus SK

In a clean and dry reactor under nitrogen, n-propyl acetate (1.69 grams)was charged along with resin VariPlus SK (1.69 grams) obtained fromDegussa. The resulting slurry was stirred and heated to 50-60° C. untilall of the resin dissolved. The reaction temperature was then cooled to25-35° C. Tetra n-propyl zirconate (4.64 grams) was added over 15minutes, and the mixture was stirred for 15 minutes. Subsequently, amixture of citric acid, mono-ethyl citrate, di-ethyl citrate andtri-ethyl citrate (hereafter referred to as “Mixture 1”) (5.23 grams)was then added over 20 minutes while the reaction temperature wasmaintained below 60° C. The total mole of Mixture 1 is around 21.00mmol, and the carboxylic acid number of Mixture 1 is around 200 mgKOH/g. When the addition was completed, the temperature was held at 60°C. for 1 hour. Thereafter, the resulting product was discharged at25-35° C. through a filter bag to obtain Product 1, a clear andlight-yellow liquid. Product 1 has a Gardner color scale of 3-5 and aBrookfield viscosity (No. 3 spindle at 60 rpm) of 30-200 mPa·s at 25° C.

Example 2: Preparation of Adhesion Promoter (Product 2) Including aReaction Product of Tetra i-Propyl Titanate, Citric Acid Ester Mixture,and Polyester Polyol

In a clean and dry reactor under nitrogen, polyester polyol (10.13grams, ca. MW 3000, the polyester polyol was BA-3000 from Shung-BangIND. CORP. which synthesized by adipic acid/butane glycol) was preheatedto 60° C. and charged. Tetra i-propyl titanate (3.00 grams) was addedover 15 minutes, and the mixture was stirred for 15 minutes. Mixture 1(5.23 grams) was then added over 20 minutes while the reactiontemperature was maintained below 60° C. When the addition was completed,the temperature was held at 60° C. for 1 hour. Thereafter, the resultingproduct was discharged at 25-35° C. through a filter bag to obtainProduct 2.

Example 3: Preparation of Adhesion Promoter (Product 3) Including aReaction Product of Tetra i-Propyl Titanate, Tartric Acid Ester Mixture,and Polyamide Resin Uni-Rez 138

In a clean and dry reactor under nitrogen, ethanol (7.40 grams) wascharged along with a polyamide resin Uni-Rez 138 (7.40 grams). Theresulting solution was stirred until all of the resin dissolved. Tetrai-propyl titanate (3.00 grams) was added over 15 minutes, and themixture was stirred for 15 minutes. Subsequently, a mixture of tartaricacid, mono-ethyl tartrate, di-ethyl tartrate and (hereafter referred toas “Mixture 2”) (3.96 grams) was then added over 20 minutes while thereaction temperature was maintained below 60° C. When the addition wascompleted, the temperature was held at 60° C. for 1 hour. Thereafter,the resulting product was discharged at 25-35° C. through a filter bagto obtain Product 3. The total mole of Mixture 2 is around 20.70 mmol,and the carboxylic acid number of Mixture 2 is around 198 mg KOH/g.

Example 4: Preparation of Adhesion Promoter (Product 4) Including aReaction Product of Tetra n-Propyl Zirconate, Malic Acid Ester Mixture,and Polyether Polyol

In a clean and dry reactor under nitrogen, polyether polyol (10.13grams, ca. MW 3000, the polyol was polypropylene glycol PT3000 from DowChemical Company) was charged. Tetra n-propyl zirconate (4.64 grams) wasadded over 15 minutes, and the mixture was stirred for 15 minutes.Subsequently, a mixture of malic acid, mono-ethyl malate, di-ethylmalate and (hereafter referred to as “Mixture 3”) (3.56 grams) was thenadded over 20 minutes while the reaction temperature was maintainedbelow 60° C. When the addition was completed, the temperature was heldat 60° C. for 1 hour. Thereafter, the resulting product was dischargedat 25-35° C. through a filter bag to obtain Product 4. The total mole ofMixture 3 is around 20.3 mmol, and the carboxylic acid number of Mixture3 is around 175 mg KOH/g.

Example 5: Preparation of Adhesion Promoter (Product 5) Including aReaction Product of Tetra i-Propyl Titanate, Malic Acid Ester Mixture,and Hydroxyl Functional Polyurethane Resin NeoRez U-471

In a clean and dry reactor under nitrogen, ethanol (7.40 grams) wascharged along with a hydroxyl functional polyurethane resin NeoRez U-471(7.40 grams). The resulting solution was stirred until all of the resindissolved. Tetra i-propyl titanate (3.00 grams) was added over 15minutes, and the mixture was stirred for 15 minutes. Mixture 3 (3.56grams) was then added over 20 minutes while the reaction temperature wasmaintained below 60° C. When the addition was completed, the temperaturewas held at 60° C. for 1 hour. Thereafter, the resulting product wasdischarged at 25-35° C. through a filter bag to obtain Product 5.

Example 6: Preparation of Ink Composition

The compositions used for forming Inks 1-9 are listed in the followingTable 1, in which Inks 1, 2, and 8 are comparative examples, and Ink 9is control example. Ink 3 was prepared by the following steps. Adispersion including denatured ethanol (18.5 g), ethyl acetate (27.5 g),nitrocellulose (9.5 g), resin VariPlus SK (2.0 g), and polyurethaneresin (15.0 g) was stirred and heat to 50-60° C., and then TiO₂ (27.5 g)was added to the dispersion. Subsequently, an adhesion promoter, Product1 (2.5 g), was added to form Ink 3. Other ink compositions (Inks 2, 4,5, 6, 7, and 8) were also formed by the processes described above;however, the adhesion promoters used for forming Inks 2, 4, 5, 6, 7, and8 were different from that for Ink 3, and Inks 1 and 9 do not includeany adhesion promoter. In Table 1, the nitrocellulose was obtained fromT. N. C. Industrial Co., Ltd., and its trade name is SS 1/8. Thepolyurethane resin was obtained from Morchem, and its trade name isTP629. VERTEC™ RJCE and VERTEC™ PI2 are commercial adhesion promoters.

TABLE 1 Ink 1 Ink 2 Ink 3 Ink 4 Ink 5 Ink 6 Ink 7 Ink 8 Ink 9 SolventDenatured ethanol (g) 18.5 18.5 18.5 18.5 18.5 18.5 18.5 18.5 18.5 Ethylacetate (g) 27.5 27.5 27.5 27.5 27.5 27.5 27.5 27.5 27.5 PolymericNitrocellulose(g) 9.5 9.5 9.5 9.5 9.5 9.5 9.5 9.5 9.5 binder ResinVariPlus SK (g) 4.5 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 Polyurethane resin(g) 15.0 15.0 15.0 15.0 15.0 15.0 15.0 15.0 15.0 Pigment TiO₂ (g) 27.527.5 27.5 27.5 27.5 27.5 27.5 27.5 27.5 Adhesion VERTEC ™ RJCE (g) NA2.5 NA NA NA NA NA NA NA promoter Product 1 NA NA 2.5 NA NA NA NA NA NAProduct 2 NA NA NA 2.5 NA NA NA NA NA Product 3 NA NA NA NA 2.5 NA NA NANA Product 4 NA NA NA NA NA 2.5 NA NA NA Product 5 NA NA NA NA NA NA 2.5NA NA VERTEC ™ PI2 (g) NA NA NA NA NA NA NA 2.5 NA Total weight (g)102.5 102.5 102.5 102.5 102.5 102.5 102.5 102.5 100

Example 7: Adhesion Test of Ink Composition

Inks 1-9 were printed on an oriented polypropylene film treated bycorona-discharge. The printed film was dried. The adhesion of each ofInks 1-9 was tested after different storage time. The adhesion testincludes the following steps. An adhesive tape (18 mm wide) is appliedto cover the surfaces of Inks 1-9 to ensure the test conditions areidentical. After a period of storage time, the adhesive tape is removedfrom the surfaces of Inks 1-9 simultaneously, and results are determinedby the percentage ink remaining in the total test area after removal ofthe adhesive tape. The adhesion test results are shown in the followingTable 2.

TABLE 2 Storage time 1 min 5 min 15 min 30 min 60 min Ink 1 10% 16% 18%22% 28% Ink 2 7% 8% 15% 26% 30% Ink 3 50% 60% 70% 85% 95% Ink 4 25% 31%42% 57% 75% Ink 5 13% 25% 31% 32% 41% Ink 6 24% 35% 48% 62% 78% Ink 733% 48% 67% 72% 79% Ink 8 40% 60% 75% 90% 95% Ink 9 5% 8% 10% 12% 15%

Example 8: Odor Test, Color Test, and Wet Crinkle Test of InkComposition

In the odor test, Inks 1-9 were printed on different orientedpolypropylene films treated by corona-discharge respectively. Theprinted films were dried and then respectively stored in sealed glassjars for 24 hours at 40° C. The odor of each of Inks 1-9 was assessed bya panel of 5 people on a scale from 1 (no perceptible odor) to 5 (verystrong odor). The data are averaged and then rounded to the nearestwhole number, and the results are listed in the following Table 3.

In the color test, Inks 1-9 were printed on different orientedpolypropylene films treated by corona-discharge respectively. Theprinted films were dried and then respectively stored in sealed glassjars for 24 hours at 40° C. The color of each of Inks 1-9 was assessedby a panel of 5 people on a scale from 1 (no perceptible color) to 5(severe yellow color). The data are averaged and then rounded to thenearest whole number, and the results are listed in the following Table3.

Further, the wet crinkle test is used to assess adhesion when a printedfilm is wet. In the wet crinkle test, Inks 1-9 were printed on differentoriented polypropylene films treated by corona-discharge respectively.The printed films were dried, and then were rubbed between the knucklesseveral times under cold running water. The wet crinkle resistance ofeach of Inks 1-9 was assessed visually by observing the undamagedremaining ink in the test area by a panel of 5 people on a scale from 1(no ink removal) to 5 (severe removal). The data are averaged and thenrounded to the nearest whole number, and the results are listed in thefollowing Table 3.

TABLE 3 Odor test Color test Wet crinkle test Ink 1 1 1 3 Ink 2 1 1 2Ink 3 1 1 1 Ink 4 1 1 1 Ink 5 1 1 2 Ink 6 1 1 1 Ink 7 1 1 1 Ink 8 4 5 1Ink 9 1 1 4

From Table 3, it can be seen that Inks 3, 4, 5, 6 and 7, which includethe adhesion promoters prepared by metal alkoxide, acid ester mixture,and polymer, are odorless and colorless, and show good wet crinkleresistance.

In view of the foregoing, the present disclosure provides inkcompositions and adhesion promoters for use in ink composition. Theadhesion promoters include a reaction product of a metal alkoxide, anacid ester mixture, and a polymer. The acid ester mixture may furtherinclude water. The manufacturing process of the adhesion promoters donot need any purification step and are simple. Moreover, the inkcompositions including the adhesion promoter of the present disclosureare odorless and colorless and show good wet crinkle resistance. It isnoted that the adhesion promoters include a mixture of many kinds ofcompounds, and therefore the properties of the adhesion promoters can beeasily adjusted to meet various requirements.

Although the present invention has been described in considerable detailwith reference to certain embodiments thereof, other embodiments arepossible. Therefore, the spirit and scope of the appended claims shouldnot be limited to the description of the embodiments contained herein.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the structure of the presentinvention without departing from the scope or spirit of the invention.In view of the foregoing, it is intended that the present inventioncover modifications and variations of this invention provided they fallwithin the scope of the following claims.

What is claimed is:
 1. An adhesion promoter comprising a reactionproduct of: (A) a metal alkoxide having a formula ofM(OR₁)(OR₂)(OR₃)(OR₄), wherein M is titanium, zirconium, or aluminum,and R₁, R₂, R₃, and R₄ are independently C₁ to C₈ alkyl group; (B) amixture of at least one alpha hydroxy acid and at least one alphahydroxy acid ester, wherein the alpha hydroxy acid is selected from thegroup consisting of glycolic acid, lactic acid, malic acid, tartaricacid, and citric acid, and the alpha hydroxy acid ester is selected fromthe group consisting of glycolic acid ester, lactic acid ester, malicacid ester, tartaric acid ester, and citric acid ester; and (C) at leastone polymer having hydroxyl group (—OH), amino group (—NH₂), carboxylgroup (—COOH), or a combination thereof.
 2. The adhesion promoter ofclaim 1, wherein the glycolic acid ester has a formula of CH₂OH(COOR₅),and R₅ is C₂ to C₆ alkyl group.
 3. The adhesion promoter of claim 1,wherein the lactic acid ester has a formula of C₂H₄OH(COOR₆), and R₆ isC₂ to C₆ alkyl group.
 4. The adhesion promoter of claim 1, wherein themalic acid ester has a formula of C₂H₃OH(COOR₇)(COOR₈), R₇ and R₈ areindependently H atom or C₂ to C₆ alkyl group, and one of R₇ and R₈ is analkyl group.
 5. The adhesion promoter of claim 1, wherein the tartaricacid ester has a formula of C₂H₂(OH)₂(COOR₉)(COOR₁₀), R₉ and R₁₀ areindependently H atom or C₂ to C₆ alkyl group, and one of R₉ and R₁₀ isan alkyl group.
 6. The adhesion promoter of claim 1, wherein the citricacid ester has a formula of C₃H₄OH(COOR₁₁)(COOR₁₂)(COOR₁₃), R₁₁, R₁₂ andR₁₃ are independently H atom or C₂ to C₆ alkyl group, and one of R₁₁,R₁₂ and R₁₃ is an alkyl group.
 7. The adhesion promoter of claim 1,wherein the mixture further comprises water.
 8. The adhesion promoter ofclaim 1, wherein the polymer is selected from the group consisting ofpolyol, polyurethane, polyurethane-urea, polyamide, polyacrylate,ketone-formaldehyde copolymer, nitrocellulose, polyvinyl alcohol,ketonic resin, alkyd, and polysaccharide.
 9. The adhesion promoter ofclaim 1, wherein the at least one polymer having the hydroxyl group hasa hydroxyl number of from about 30 mg KOH/g to about 500 mg KOH/g. 10.The adhesion promoter of claim 1, wherein the at least one polymerhaving the amino group has an amine value of from about 3.5 mg KOH/g toabout 15 mg KOH/g.
 11. The adhesion promoter of claim 1, wherein a ratioof a number of the hydroxyl group of the at least one polymer having thehydroxyl group to a number of M of the metal alkoxide is 0.25-4:1. 12.The adhesion promoter of claim 1, wherein a ratio of a number of theamino group of the at least one polymer having the amino group to anumber of M of the metal alkoxide is 0.25-4:1.
 13. The adhesion promoterof claim 1, wherein the mixture has a carboxylic acid number of fromabout 50 mg KOH/g to about 400 mg KOH/g.
 14. The adhesion promoter ofclaim 1, wherein a ratio of a total mole of the at least one alphahydroxy acid and the at least one alpha hydroxy acid ester to a mole ofthe metal alkoxide is 0.2 to 4:1.
 15. An ink composition comprising: apigment; a polymeric binder; a solvent for the polymeric binder; and theadhesion promoter of claim
 1. 16. The ink composition of claim 15,wherein the adhesion promoter is present at a concentration of from 1%to 20% by weight, based on the total weight of the ink composition. 17.The ink composition of claim 15, wherein the polymeric binder has atleast one functional group selected from the group consisting ofhydroxyl group (—OH), amino group (—NH₂), carboxyl group (—COOH),cyanate group (—NCO), and ester group.